Ice cutter for monopod drilling platform

ABSTRACT

A monopod drilling platform having cylindrical structural column extending vertically between a drilling deck and a submerged base in which a concentric sleeve surrounds the column and is rotatably supported from outside of the sleeve, the sleeve having ice cutter arms projecting radially from the outer surface thereof. Both axial thrust and centering of the sleeve are provided by a plurality of rollers mounted around the outside of the sleeve, the roller engaging a conical surface projecting outwardly from the sleeve. The rollers are individually adjustable and removable without interrupting rotation of the sleeve by drive means mounted on the deck.

United States Patent July 15, 1975 Smith l l ICE CUTTER FOR MONOPOI)DRILLING L TFORM Primary E.taminerTrygve M. Blix A AssistantE.t'aminerStuart M. Goldstein [75] Inventor: Charles Glenddlfi Cdhf'Attorney Agent, or Firm-Christie, Parker & Hale [73] Assignees Sea-LogCorporation, Pasadena.

Calif [57] ABSTRACT [22] Filed; Apr. 8, 1974 A monopod drilling platformhaving cylindrical structural column extending vertically between adrilling [Z1] Appl- N05 459,029 deck and a submerged base in which aconcentric sleeve surrounds the column and is rotatably sup- 52 5 3 1142; 4 299/24 ported from outside of the sleeve the sleeve having 51 Int.ct .i B63!) 35/12 ice Cutter firms Projecting radially from the Outer WP[58] Field of Search H H4/5 D4UU4142; face thereof. Both axial thrustand centering of the 61/465 1 R; 299/24 25 sleeve are provided by 11plurality of rollers mounted around the outside of the sleeve. theroller engaging a [56] References Cited conical surface projectingoutwardly from the sleeve UNITED STATES PATENTS The rollers areindividually adjustable and removable without interrupting rotation ofthe sleeve by drive 3669.052 (1/l972 Schlrtzlnger l 14/42 means mountedOn the deck 3,696,624 lU/l972 Bennett w. ll4/42 1759046 9/1973 Anders .7l l4/4l 8 Claims. 6 Drawing Figures :r c: u c u a 8 u u a a n a aPATENTH] JUL 1 5 I975 SHEET ICE CUTTER FOR MONOPOD DRILLING PLATFORMFIELD OF THE INVENTION This invention relates to drilling platforms foroperation in arctic waters, and more particularly, is concerned with anice cutting mechanism for a monopodtype structure.

BACKGROUND OF THE INVENTION With the discovery of oil in the arcticregions of the world, there has developed a need for a drilling platformcapable of operating in icy waters. The forces created by lateral andvertical movement of ice floes can damage or overturn an offshoredrilling platform. Various types of mechanisms have heretofore beenproposed for cutting, melting, or otherwise diverting the ice fromimposing destructive forces on the supporting structure of off-shoredrilling platforms. See, for example, US. Pat. No. 3,669,052.

Such prior art systems have included the use of high speed rotatingcutters for comminuting the ice as it moves toward the platformsupports. Generally the cutters have been spaced about the supportingstructure so as to operate effectively with ice movement from anydirection. Some designs include cutters which rotate concentricallyaround the vertical axis of the supporting structure. However,concentrically operated cutters have presented problems in effectivelysupporting and driving the concentric cutters so as to withstand theforces and transmit the power required. For example, it has beennecessary to adjust the vertical position of the cutters to accommodatedifferent levels and thicknesses of ice. Such arrangements have beenpractical only where the supporting columns are relatively small indiameter.

The present invention provides an improved ice cutting apparatus foroperation with a monopod-type structure, in which all drilling takesplace through a central opening in a single column that also providesstructural support for the drilling deck and associated superstructureabove the water from a submerged base. Such a column is, of necessity,of relatively large diameter, presenting unique problems in rotatablysupporting thereon a concentric cutter strong enough and driven withsufficient torque to handle heavy ice floes.

SUMMARY OF THE INVENTION In brief, the present invention provides an icecutting mechanism for a monopod platform in which the cutters aremounted as radial arms on a sleeve that is concentric with thesupporting column. The sleeve may extend substantially the full lengthof the column but is supported at either end on a plurality of rollerswhich engage a conical surface projecting from the outside of thesleeve. The rollers are individually mounted and adjustable to align thesleeve concentrically with the supporting column. In one embodiment, therollers with their mounting structure are positioned inside a housingbeneath the deck for protection from the elements.

In an alternative embodiment the rollers are located adjacent the lowerend of the sleeve and mounted on the lower hull structure below thewater. The rollers are individually adjustable to equalize the load oneach bearing, and are individually replaceable to permit maintenance andindividual replacement to go forward without interruption of the cutterdrive mechanism.

DESCRIPTION OF THE DRAWINGS For a better understanding of the invention.reference should be made to the accompanying drawings, wherein:

FIG. I is an elevational view of a monopod drilling structureincorporating the features of the present invention;

FIG. 2 is a sectional view taken substantially on a line 22 of FIG. 1;

FIG. 3 is a partial sectional view taken on a line 3-3 of FIG. 2;

FIG. 4 is a detailed sectional view of the supporting roller assembly;

FIG. 5 is a sectional view taken substantially on a line 5-5 of FIG. 4;and

FIG. 6 is a detailed sectional view of an alternative embodiment.

DETAILED DESCRIPTION Referring to the drawings in detail, the numeral l0indicates generally the base of a drilling platform. The base is in theform of a hull constructed of bulkheads and outer plates, providing asubstantially watertight structure which may be ballasted to rest on thesea bottom at the drilling location or which may be sufficiently buoyantto float beneath the surface as a semisubmersible. A superstructure 12providing an upper drilling deck I4 is supported above the water surfacefrom the base I0 by a single vertical column indicated generally at 16.Drilling is accomplished from the drilling deck 14 down through thecolumn and base into the sea floor by means of conventional drillingequipment including a drilling derrick 18 mounted on the drilling deck14. As shown in the cross-sectional view of FIG. 2, the column consistsof an outer stationary cylindrical shell 20 which is rigidly attached atits lower end to the bottom of the base 10. Inside the column 20 is acylindrical casing 22 through which access to the ocean floor from thedrilling deck is provided. The opening through the casing is referred toas the "moon pool" The casing 22 is preferably offset from the outerstationary cylinder 20 to provide a larger working space for men andequipment between the drilling deck and the subsurface base.

Surrounding the outside of the cylinder 20 and concentric therewith, isa cylindrical sleeve 24. The sleeve 24 is rotatably supported and drivenfrom the upper superstructure 12 to permit continuous rotation of thesleeve 24 around the outside of the cylinder 20. Individual cutter arms26 are secured to the outer surface of the sleeve 24. The cutter armsare positioned around the complete circumference of the sleeve 24 andare positioned vertically substantially the full length of the column16.

The cutter sleeve 24 is rotatably supported at its upper end by means ofa segmented collar 30. The segmented collar provides a conicalsupporting surface 32 extending continuously and completely around thetop of the sleeve. The axis of revolution of the conical surface iscoaxial with that of the cylinder 20, the conical surface extending atan acute angle upwardly and outwardly from the sleeve. A plurality ofroller assemblies 34 are mounted on supporting members 36 attached toand extending downwardly from the structure supporting the drilling deck14. Details of the roller assembly are described below in connectionwith FIGS. 4 and 5. While as few as three roller assemblies would permitbalanced support, because of the large load and to provide sufficientmargin of safety, typically ninety or more roller assemblies spaced at afoot or less apart are provided.

The roller assemblies 34 include rollers which engage the conicalsurface 32. The rollers, by having their roll axes intersecting the axisof rotation of the cutter sleeve at the same acute angle as the conicalsurface 32, both support the weight of the sleeve and center the sleeveabout its axis of rotation. Rotation is imparted to the cutter sleeve 24by means of a segmented ring gear 40 attached to the outer circumferenceof the cutter sleeve just below the upper end thereof. The ring gear inturn is engaged by one or more drive assemblies, each including anengine 42 connected through a clutch 44 to a gearbox 46, all of which ismounted on a lower deck 48 within the upper housing 12 of the drillingplatform. The gearbox 46 drives a pinion gear 50 that is in drivingengagement with the ring gear 40. A number of such engine and gearboxdrives may be angularly spaced about the periphery of the ring gear 40,permitting the amount of horsepower driving the cutter sleeve to bevaried according to the load conditions by increasing or decreasing thenumber of engines operat- Referring to FIGS. 4 and in detail, the rollersupport assembly is shown in more detail. The collar 30 is made up of aplurality of abutting sectors having an inner cylindrical surface whichengages the outer surface of the upper end of the cutter sleeve 24. Thecollar sectors are held in place by screws 52 which extend throughflange portions of the collar sectors and threadedly engage the cuttersleeve. The abutting collar sectors provide a continuous annular conicalsurface 32 extending completely around the cutter sleeve 24. Each rollerassembly 34 including a supporting bracket 54 which is bolted to thesupporting members 36 by removable bolts (not shown). Each bracket 54has a lower flange 56 through which extends a threaded opening 58. Theaxis of the opening 58 extends substantially perpendicular to theconical surface 32. An adjustable support and guide member 60 threadedlyengages the opening 58. The axial position of the member 60 can bechanged by screwing it in and out of the opening 58. A lockscrew 62extends through a selected one of a plurality of notches 63 positionedaround the outer periphery of the adjusting member 60. The screw 62threadedly engages the flange 56.

A yoke 64 has an integral supporting shaft 66 journaled for rotation ina bore 68 extending through the adjusting member 60. Axial position ofthe yoke 64 is made adjustable by spring means positioned between theyoke 64 and the adjusting member 60. The spring is preferably in theform of at least one pair of dished spring washers 70, commonly referredto as Belleville" washers.

The yoke supports a shaft 72 on which is journaled a roller 74 by meansof a pair of tapered roller bearings 76. Shaft 72 is held in place onthe yoke by means of a flange 78 at one end and a nut 80 whichthreadedly engages the other end. The yoke 64 is provided with a lug 82on one side which engages a slot 84 formed adjacent the upper end of thesupporting bracket 54. The

lug 84 prevents any rotation of the roller assembly about the axis ofthe supporting shaft 66.

In a typical installation the cutter sleeve may have an outer diameterof the order of 20 feet, for example, thus the supporting column mayhave a circumference of 65 feet or greater. As many as ninety rollerassemblies may be positioned around the circumference of the collar toshare the load of the cutter sleeve. By way of example only, thevertical load imposed by the rotating cutter assembly on the supportingrollers may be in the order of 400 tons. Each of the rollers can beadjusted so as to distribute the load substantially equally among all ofthe rollers. However, it is possible for the cutter sleeve to beoperated with one or more of the rollers not taking any of the load.Thus, extremely high reliability is achieved since, if any one of theroller assemblies fails, it can be removed and replaced withoutinterrupting the operation of the cutters. A defective roller assemblycan be easily removed by removing the adjusting member 60. The rollerassembly 34 can then be cocked to one side and lifted out of opening 58,permitting a new assembly to be inserted in its place. The location ofthe roller assemblies within the upper housing 12 makes them readilyaccessible during operation.

The angle of the rollers is such that they are capable of resisting notonly vertical forces due to the weight or other axial thrust loads onthe cutter sleeve, but also the rollers resist radial forces on thesleeve and act to center the sleeve in concentric position with respectto the supporting cylindrical structure 20. However, it is preferable toprovide a nylon or other suitable bearing material in the annular spacebetween the inside of the cutter sleeve 24 and outside of the cylinder20 adjacent the upper end of the sleeve. The nylon bearing includes abase member secured to the cylindrical member 20 with a nylon facing 92spaced from the inside wall of the cutter sleeve 24. The nylon bearingmay either be in the form of a continuous ring or in the form ofangularly spaced individual segments positioned around the circumferenceof the cylindrical member 20. The nylon bearing is provided only as asafety feature and normally would not be under radial load.

In addition, a nylon bearing 96 is provided as a spacer between thecylindrical member and the sleeve at the lower end of a cutter sleeve 24for transferring a por tion of the lateral loads from the sleeve to thesupporting column.

An alternative embodiment is shown in FIG. 6 in which the bearingsupport and drive for the sleeve 24 are located at the lower end of thesleeve. The motors for driving the sleeves are located within the lowerhull 10. Output drive shaft, such as indicated at 100, passes through aplate 102 within the lower hull 10 through a suitable bearing 104. Theupper end of each shaft terminates in a pinion gear 106 which engages aring gear 108 extending around the outside of the lower end of thesleeve 24. A plurality of drive shafts 100 and pinion gears 106 arepositioned at circumferentially spaced points around the ring gear 108.

The bearing support assembly for the sleeve 24 includes a base plate 110which is supported from the plate 102 by an outer support plate 112 anda plurality of radially extending plates, one of which is indicated at114. A plurality of roller assemblies, one of which is indicated at 116,similar to the roller assembly 34 described above, are individuallysupported from the top of the plate by an adjustable mounting assemblyindicated generally at 118. p

The adjustable mounting assembly 118 includes a base 120 which is boltedor otherwise secured to the top of the plate 110. A hinge plate 122 ispivotally joined to the base 120 by a hinge pin 124. The outer end ofthe hinge plate 122 is adjustably supported from the base 120 by an arm125 pivotally joined to the base 120 by a hinge pin 126. The outer endof the arm is threaded, as indicated at 128. A coupling unit has asleeve portion which slips over the threaded end of the arm 124 and isheld between two nuts 132 and 134 which engage the threaded end 128 ofthe arm 124 and clamp the sleeve portion of the coupling unit. The outerend of the hinge plate 122 in turn is pivotally connected to thecoupling unit 130 by a pin 136. Thus by adjusting the nuts 132 and 134,the angle of the hinge plate 122 relative to the base 120 can be varied.

The roller assembly 116 includes a roller 138 which is in rolling with aconical surface 140 provided by a support bracket 142 which extendsaround the periphery of the sleeve 24.

The roller assembly 116 includes one or more pairs of dished springelements 144 which are placed under compression by the load of thesleeve 24. The load is equalized among a plurality of roller assembliesby a threaded guide member 146 which engages a threaded opening in thehinge plate 122. Rotation of the threaded guide member by a detent knob148 moves the roller assembly 116 in a direction perpendicular to theconical surface 140. The detent knob 148 is locked in position by adetent member 150 which is anchored to a shaft 152 by a clamping screw154. The shaft 152 also passes through a flange 156 integral with theroller assembly 116 so as to keep the roller assembly in properalignment. An indexing plate is held between the lower end of the springelements and the knob 148 to provide an indication of the degree towhich the spring elements are compressed by adjust ment of the knob 148.This permits each roller assembly 116 to be adjusted to equalize theload on each assembly.

Individual roller assemblies 116 can be removed by loosening the knob148 until the load on the roller is relieved. The pin 136 is thenwithdrawn, allowing the hinge plate 122 to be backed off sufficientlyfor the roller assembly to be lifted from the threaded guide member 146.A shroud 158 may be provided which surrounds the roller assembly 116 toprevent pieces from a broken bearing falling into the gears.

The entire roller assembly is positioned in the watertight lower hull10. the sleeve 24 extends down through the top of the hull through asuitable seal (not shown) to prevent water from entering around theoutside of the sleeve.

What is claimed is:

1. A drilling platform for operation in arctic waters comprising:

a work platform positioned above the water, subsurface support meansincluding a vertically extending cylindrical member on which the workingplatform is supported, and ice cutting means mounted on the cylindricalmember, the ice cutting means including a concentric sleeve extendingaround the cylindrical member, bearing means rotatably supporting thesleeve on the cylindrical member, a plurality of radially projectingcutter arms mounted on the sleeve, drive means for rotating the sleeveabout the cylindrical member. the bearing means comprising a pluralityof rollers spaced around the outer circumference of the sleeve, andmeans individually supporting the rollers in fixed relation to thesub-surface support means with the axes of the rollers extendingradially of the sleeve at an acute angle to the axis of the rotation ofthe sleeve, the sleeve having a conical surface extending outwardly ofthe sleeve at said acute angle and in contact with said rollers.

2. Apparatus of claim 1 wherein each individual roller supporting meansincludes spring means for yieldably supporting the associated rolleralong an axis perpendicular to the conical surface.

3. Apparatus of claim 2 wherein each individual roller supporting meansis detachable.

4. Apparatus of claim 1 wherein the drive means includes a ring gearextending around the outside of the sleeve, and a plurality of driveunits supported from the working platform and spaced around theperiphery of the ring gear, each drive unit having a pinion engaging thering gear to drive the ring gear and sleeve.

5. in a drilling platform having a lower submerged hull, an upper deckstructure, and at least one cylindrical supporting column extendingvertically between the lower hull and upper deck structure, ice cuttingapparatus comprising a tubular sleeve concentrically positioned on thesupporting column, the upper end extending up to the deck structure andthe lower end extending down to the hull, annular bearing means betweenthe column and inside of the sleeve adjacent the lower end of thesleeve, and thrust bearing means extending around the outside of theupper end of the sleeve, support means rigidly secured to the upper deckstructure extending under the thrust bearing means for supporting thethrust bearing means from the deck structure, and means extendingradially from the sleeve above the thrust bearing means for transferringthe weight of the sleeve to the thrust bearing means, a plurality of icecutters projecting from the sleeve below the thrust bearing, and drivemeans supported from the upper deck and engaging the sleeve in drivingrelationship.

6. In a drilling platform having a lower submerged hull, an upper deckstructure, and at least one cylindrical supporting column extendingvertically between the lower and upper hulls, ice cutting apparatuscomprising a tubular sleeve concentrically positioned on the supportingcolumn, annular bearing means between the column and inside of thesleeve adjacent the lower end of the sleeve, and thrust bearing meansextending around the outside of the upper end of the sleeve, supportmeans secured to the upper deck structure extending under the means forsupporting the thrust bearing means, and means extending radially fromthe sleeve above the thrust bearing means for transferring the weight ofthe sleeve to the thrust bearing means, a plurality of ice cuttersprojecting from the sleeve below the thrust bearing, and drive meanssupported from the upper deck and engaging the sleeve in drivingrelationship, the thwst bearing means including a plurality of rollersspaced around the outer circumference of the sleeve, and meansindividually supporting the rollers in fixed relation to the supportmeans with the axes of the rollers extending radially of the sleeve atan acute angle to the axis of rotation of the sleeve, the sleeve having3 ,894,504 7 8 a conical surface extending outwardly of the sleeve atpendicular to the conical surface. said acute angle and in contact withsaid rollers.

7. Apparatus of claim 6 wherein each individual roller supporting meansincludes spring means for yieldably supporting the associated rolleralong an axis per- 8. Apparatus of claim 7 wherein each individualroller supporting means is detachable.

1. A drilling platform for operation in arctic waters comprising: a workplatform positioned above the water, sub-surface support means includinga vertically extending cylindrical member on which the working platformis supported, and ice cutting means mounted on the cylindrical member,the ice cutting means including a concentric sleeve extending around thecylindrical member, bearing means rotatably supporting the sleeve on thecylindrical member, a plurality of radially projecting cutter armsmounted on the sleeve, drive means for rotating the sleeve about thecylindrical member, the bearing means comprising a plurality of rollersspaced around the outer circumference of the sleeve, and meansindividually supporting the rollers in fixed relation to the sub-surfacesupport means with the axes of the rollers extending radially of thesleeve at an acute angle to the axis of the rotation of the sleeve, thesleeve having a conical surface extending outwardly of the sleeve atsaid acute angle and in contact with said rollers.
 2. Apparatus of claim1 wherein each individual roller supporting means includes spring meansfor yieldably supporting the associated roller along an axisperpendicular to the conical surface.
 3. Apparatus of claim 2 whereineach individual roller supporting means is detachable.
 4. Apparatus ofclaim 1 wherein the drive means includes a ring gear extending aroundthe outside of the sleeve, and a plurality of drive units supported fromthe working platform and spaced around the periphery of the ring gear,each drive unit having a pinion engaging the ring gear to drive the ringgear and sleeve.
 5. In a drilling platform having a lower submergedhull, an upper deck structure, and at least one cylindrical supportingcolumn extending vertically between the lower hull and upper deckstructure, ice cutting apparatus comprising a tubular sleeveconcentrically positioned on the supporting column, the upper endextending up to the deck structure and the lower end extending down tothe hull, annular bearing means between the column and inside of thesleeve adjacent the lower end of the sleeve, and thrust bearing meansextending around the outside of the upper end of the sleeve, supportmeans rigidly secured to the upper deck structure extending under thethrust bearing means for supporting the thrust bearing means from thedeck structure, and means extending radially from the sleeve above thethrust bearing means for transferring the weight of the sleeve to thethrust bearing means, a plurality of ice cutters projecting from thesleeve below the thrust bearing, and drive means supported from theupper deck and engaging the sleeve in driving relationship.
 6. In adrilling platform having a lower submerged hull, an upper deckstructure, and at least one cylindrical supporting column extendingvertically between the lower and upper hulls, ice cutting apparatuscomprising a tubular sleeve concentrically positioned on the supportingcolumn, annular bearing means between the column and inside of thesleeve adjacent the lower end of the sleeve, and thrust bearing meansextending around the outside of the upper end of the sleeve, supportmeans secured to the upper deck structure extending under the means forsupporting the thrust bearing means, and means extending radially fromthe sleeve above the thrust bearing means for transferring the weight ofthe sleeve to the thrust bearing means, a plurality of ice cuttersprojecting from the sleeve below the thrust bearing, and drive meanssupported from the upper deck and engaging the sleeve in drivingrelationship, the thrust bearing means including a plurality of rollersspaced around the outer circumference of the sleeve, and meansindividually supporting the rollers in fixed relation to the supportmeans with the axes of the rollers extending radially of the sleeve atan acute angle to the axis of rotation of the sleeve, the sleeve havinga conical surface extending outwardly of the sleeve at said acute angleand in contact with said rollers.
 7. Apparatus of claim 6 wherein eachindividual roller supporting means includes spring means for yieldablysupporting the associated roller along an axis perpendicular to theconical surface.
 8. Apparatus of claim 7 wherein each individual rollersupporting means is detachable.